The purpose of this study is to obtain long-term safety and tolerability data for the combination of ddl and hydroxyurea with or without other antiretroviral agents. The proposed study will provide the opportunity to gather additional data on subjects who are currently participating in ACTG 307, as well as provide the opportunity to follow non-307 subjects who have been on a ddl/HU regimen. Subjects considered for this rollover must either have HIV-1 RNA levels below 5,000 copies per mL or have had at least a 10 fold reduction in HIV RNA level from their baseline prior to treatment. Subjects on this rollover protocol have the opportunity to add additional antiretroviral medications to their treatment based on consultation with their HIV care providers. There are two substudies proposed with this study. The Immunology substudy is an inherent part of the main study, and will compare the effects of combination therapy versus ddl monotherapy on various immunologic parameters. The second substudy is optional, and will examine the level of viral suppression in blood, genital secretions, and/or CSF, and in quiescent latently infected CD4 cells. A separate consent will be required for this substudy.